This invention relates to the field of measuring and marking tools such as roofers""squares having a right triangle configuration comprising a first and second side which intersect at a right angle and a third side forming the hypotenuse, a ledge or T-bar along one of the first and second sides which projects above and below the upper and lower surfaces of the square, and with linear measurement and degree markings on both surfaces of the square along respective edge portions. In particular, this invention relates to such tools or squares in which positioning elements are provided to position the tool in selected marking positions and to hold marking pencils in position for marking lumber to be cut for rafters and other parts of the roofing or construction framework.
A number of builder""s measurement and marking tools such as roofing squares of the right triangle type are known to the prior art. Those known to the inventor herein are shown and described in the following United States patents which are readily available to the public in a number of locations throughout the United States: U.S. Pat. Nos. 4,513,510 and 4,742,619 both of which have been assigned to the assignee of the present invention described herein,and the patents cited in those cases which are; U.S. Pat. Nos. 175,113; 183,387; 864,096; 1,001,316; 1,014,453; 2,805,484; 3,623,232; 4,244,105; 265,383; 437,870; 1,249,132; 2,076,300; and 3,178,826.
The builder""s measurement and marking tool in accordance with a preferred embodiment of the present invention has a right triangle configuration, comprising a first and second side edge which intersect at a right angle and a third side edge which forms the hypotenuse. A T-bar extends along the first side edge and projects upwardly about a quarter inch from the upper surface of the square as well as downwardly about a quarter inch from its lower or downwardly facing surface. A linear scale in inches is provided along the second side edge, starting at the intersection of the first and second side edges with markings at eighth of an inch and numerals starting with the number one to indicate each inch. Such markings are provided along the second side edge on both oppositely facing surfaces of the square. The wall portion of the second side edge between the upper and lower surfaces of the square is smooth and planar to permit use as a straight edge for sliding a pencil therealong to mark a straight line. A diamond shape aperture is provided, with one of its points at the three and a half inch mark of the aforesaid markings along the second side edge, which is three and half inches from the T-bar along the first side edge. This is the width of a conventional two by four piece of lumber and is thus useful for marking such distance on pieces of lumber for use in roof construction and other types of building construction. The diamond configuration of the aperture provides sufficient space for the elongated lead point of a carpenter""s pencil to extend through the square to mark on the surface of the piece of lumber below, and it holds such elongated lead point steady while the workman slides the square with pencil in place along the surface of the work piece being marked.
One particularly advantageous use of the diamond shaped aperture of this invention is in marking out seat cuts, or xe2x80x9cbirdsmouths,xe2x80x9d on lumber to be used for rafters. The term xe2x80x9cbirdsmouthxe2x80x9d is commonly used in the trade to indicate the triangular cut-out portion of a rafter which seats on the ridge plate of the building wall, with one side edge of the cut-out extending vertically in abutment against the vertical side wall of the ridge plate and the other side edge of the cut-out extending horizontally resting on and against the upwardly facing, horizontally extending surface of the ridge plate, while the rafter itself extends upwardly from the ridge plate at a pre-determined diagonal.
To mark the birdsmouth on a piece of lumber to be used for a rafter using the square with the diamond aperture in accordance with this invention, a plumb line is first marked on the piece of lumber at a desired distance in from the lower rafter end depending on the overhang desired. The plumb line extends vertically when the piece of lumber is positioned to extend at the desired pre-determined diagonal The square is then placed on the piece of lumber with the T-bar along the first side edge of the square abutting against a side of the piece of lumber or work piece in which the birdsmouth is to be cut at which time the second side edge of the square having the diamond shaped aperture at its three and a half inch location extends inwardly of such work piece. A workman can then slide the square along such side edge of the work piece, until the diamond shaped aperture intersects the plumb line. The square is then rotated with the diamond shaped aperture over the plumb line until the plumb line intersects the opposite points of the diamond shaped aperture which lie on an imaginary line that extends normal to the second side edge of the square. The straight second edge of the square thus extends at a ninety degree angle from the plumb line, along which a cut-out line can be marked on the work piece from the plumb line to the side edge of the work piece. The birdsmouth can then be cut first along the plumb line from the side edge of the work piece to its intersection with the cut-out line, after which a second cut can be made in the work piece along the said cut-out line from its side edge to the plumb line and to the end of the first cut therealong.